Scaling of the fingering pattern of an impacting drop

We have studied experimentally the fingered splatter left behind after a liquid drop impacts a solid surface at high values of the Reynolds and Weber numbers. The viscosity and surface tension of the liquid was varied by using several different fluid mixtures. The surface chosen was a thick paper sheet, on which the drop left a clear signature of the impact pattern. The maximum spreading of the fluid and the number of fingers seem to scale with an Impact Reynolds number, U(π² ρD³/16σ)^1/4/ν^1/2, where U is the impact velocity, ν the kinematic viscosity of the fluid, ρ the fluid density, σ the surface tension and D the drop diameter. The number of fingers is weakly dependent on the surface tension and depends primarily on the inertial-viscous interaction.